This invention relates to a system for controlling the motion of a robot. More particularly, this invention relates to such a motion control system which includes a velocity monitoring device.
Motion control systems for industrial robots are known wherein a control unit transforms a velocity reference value, defined with respect to fixed spacial coordinates, into command signals corresponding to respective axes of rotation of individual axis drives of the industrial robot. In such motion control systems, means are generally provided to shut down the drives in the event that maximum motion velocities of the robot are exceeded.
In industrial robots, especially in programming or testing work in the working range, it is necessary to ensure that velocities of the various robot parts do not exceed 25 cm per second. This limitation on velocity is possibly exceeded not only owing to the provision of excessive reference velocity values but also owing to disturbances or miscalculations in the control unit.
In known motion control systems for industrial robots, the limitation of velocities within acceptable ranges is accomplished either by inching at reduced power levels and/or by monitoring the velocities of individual drives about respective axes of rotation. A disadvantage of the second mode of implementation is that the resulting velocity of a free end of the robot may become excessively high although the angular velocities of individual robot parts about respective axes of rotation are kept within acceptable limits or ranges.
An object of the present invention is to provide an improved robot motion control system of the above-described type.
Another object of the present invention is to provide such an improved motion control system wherein the exceeding of a predetermined maximum translational velocity is prevented.